The Gene Silencing Section (GSS) aims to be a center of excellence and expertise within CCR for the study and application of RNAi in mammalian cells. The scientific and clinical developments in the field of RNAi are rapidly impacting our understanding of the role of RNA silencing mechanisms on the control of normal and disease related gene expression, including cancer. Further, technological developments utilizing RNAi analysis to study gene function, the development of new model systems, improved understanding of drug: target interactions and target identification through large scale-screening, including whole genome, RNAi approaches (siRNA and shRNA) are now highly realistic. The GSS continues to contribute the CCR RNAi initiative in a number of ways including: (A) Out reach and assistance: We have delivered a number of lectures to interested CCR laboratories, Branches and CCR Faculty/Working Group/Program based groups with the aim of educating individuals as to the current status of the RNAi field and the role of GSS specifically. Time has been spent advising to various degrees investigators from many CCR laboratories and Branches including, CTB, CCBB, EIB, GB, HAMB, NOB, POB, UOB, LBC, LCP, LCB, LCRC, LCMB, LCCTP, LCO, LEC, LEI, LG, LHC, LICB, LM, LMB, LMI, LTIB, LMP, LP, LPG, SBL. (B) Information technology: Critical to the dissemination of RNAi technology will be computer-based access to RNAi-related information. We our now posting regular updates to the GSS website within the OSTP, OD, CCR web-site reporting siRNA characterization data that is available to CCR investigators and we envisage shortly introducing pages describing access to shRNA resources and standardized protocols. In addition, Dr. Caplen has had input into the development of a centralized RNAi database at NCBI which should become fully operational in Fall 2005. (C) Initial Gene Targets and expansion to whole genome analysis: During Fall 2003 and early 2004 an extensive out-reach program was conducted to identify key gene targets where RNAi analysis would improve our understanding of the role of a gene/protein in the cancer process and or as an anti-cancer target. As will be described below and within other projects GSS has now established RNAi resources, appropriate assays and down-stream functional analysis for a significant proportion of these targets. Success with this initial analysis has now given us sufficient confidence to begin the process of expanding our remit to consider whole genome RNAi approaches. (D) RNAi resources: Synthetic siRNAs to approximately 400 cancer-associated genes are now available to GSS and we have completed characterization of the RNAi mediated by the siRNAs corresponding to 85 of these genes. CCR investigators can access this characterization data using an intramural MTA mechanism. During FY05 we supplemented our synthetic siRNA resources with 300 shRNA clones purchased to support a specific collaborative project. Recent advancements in shRNA resources developed by the extramural community and available through purchase have given us sufficient confidence to invest in a whole genome human shRNA library. Work on the establishment of this library as a working entity will begin in Fall 2005. (E) Relationship to other CCR initiatives: We continue to also interact with other CCR initiatives, programs, faculties and groups including MTDP/MTP, DTP, RTP, MWG, ABCC and the AMI.